Re: [RFC PATCH v3.1 12/27] mmc: sdhci-uhs2: add reset function

[AKASHI Takahiro <takahiro.akashi@linaro.org>]

On Thu, Nov 26, 2020 at 10:16:11AM +0200, Adrian Hunter wrote:
> On 6/11/20 4:27 am, AKASHI Takahiro wrote:
> > Sdhci_uhs2_reset() does a UHS-II specific reset operation.
> > 
> > Signed-off-by: Ben Chuang <ben.chuang@genesyslogic.com.tw>
> > Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> > ---
> >  drivers/mmc/host/sdhci-uhs2.c | 49 +++++++++++++++++++++++++++++++++++
> >  drivers/mmc/host/sdhci-uhs2.h |  1 +
> >  drivers/mmc/host/sdhci.c      |  3 ++-
> >  drivers/mmc/host/sdhci.h      |  1 +
> >  4 files changed, 53 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/mmc/host/sdhci-uhs2.c b/drivers/mmc/host/sdhci-uhs2.c
> > index 08905ed081fb..e2b9743fe17d 100644
> > --- a/drivers/mmc/host/sdhci-uhs2.c
> > +++ b/drivers/mmc/host/sdhci-uhs2.c
> > @@ -10,6 +10,7 @@
> >   *  Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
> >   */
> >  
> > +#include <linux/delay.h>
> >  #include <linux/module.h>
> >  
> >  #include "sdhci.h"
> > @@ -49,6 +50,54 @@ void sdhci_uhs2_dump_regs(struct sdhci_host *host)
> >  }
> >  EXPORT_SYMBOL_GPL(sdhci_uhs2_dump_regs);
> >  
> > +/*****************************************************************************\
> > + *                                                                           *
> > + * Low level functions                                                       *
> > + *                                                                           *
> > +\*****************************************************************************/
> > +
> > +/**
> > + * sdhci_uhs2_reset - invoke SW reset
> > + * @host: SDHCI host
> > + * @mask: Control mask
> > + *
> > + * Invoke SW reset, depending on a bit in @mask and wait for completion.
> > + */
> > +void sdhci_uhs2_reset(struct sdhci_host *host, u16 mask)
> > +{
> > +	unsigned long timeout;
> > +
> > +	if (!(host->mmc->caps & MMC_CAP_UHS2))
> 
> Please make a helper so this can be like:
> 
> 	if (!sdhci_uhs2_mode(host))
> 
> The capability will be always present for hosts that support UHS2, but not
> all cards support UHS2 mode.  I suggest just adding a bool to struct
> sdhci_host to keep track of when the host is in UHS2 mode.

Given the fact that UHS-2 host may (potentially) support a topology like
a ring, this kind of status should be attributed to a card (structure)
rather than a host.

I'm asking Ben to modify the way how the current mode be managed
in both 'core' side and 'host' side.
That is why I marked "TODO" in many places to check the mode.

So I'd defer the change until his rework be done.


> > +		return;
> > +
> > +	sdhci_writew(host, mask, SDHCI_UHS2_SW_RESET);
> > +
> > +	if (mask & SDHCI_UHS2_SW_RESET_FULL) {
> > +		host->clock = 0;
> > +		/* Reset-all turns off SD Bus Power */
> > +		if (host->quirks2 & SDHCI_QUIRK2_CARD_ON_NEEDS_BUS_ON)
> 
> I would prefer not to support any legacy quirks that we do not need right
> now.  Just be sure to add a comment somewhere listing which quirks are not
> supported for UHS2 host controllers.

No strong opinion. I'd defer to you.

> > +			sdhci_runtime_pm_bus_off(host);
> > +	}
> > +
> > +	/* Wait max 100 ms */
> > +	timeout = 10000;
> > +
> > +	/* hw clears the bit when it's done */
> > +	while (sdhci_readw(host, SDHCI_UHS2_SW_RESET) & mask) {
> 
> This kind of loop can now be done with read_poll_timeout_atomic(sdhci_readw,
> ..., host, SDHCI_UHS2_SW_RESET)

Okay.

-Takahiro Akashi

> > +		if (timeout == 0) {
> > +			pr_err("%s: %s: Reset 0x%x never completed.\n",
> > +			       __func__, mmc_hostname(host->mmc), (int)mask);
> > +			pr_err("%s: clean reset bit\n",
> > +			       mmc_hostname(host->mmc));
> > +			sdhci_writeb(host, 0, SDHCI_UHS2_SW_RESET);
> > +			return;
> > +		}
> > +		timeout--;
> > +		udelay(10);
> > +	}
> > +}
> > +EXPORT_SYMBOL_GPL(sdhci_uhs2_reset);
> > +
> >  /*****************************************************************************\
> >   *                                                                           *
> >   * Driver init/exit                                                          *
> > diff --git a/drivers/mmc/host/sdhci-uhs2.h b/drivers/mmc/host/sdhci-uhs2.h
> > index b9529d32b58d..7bb7a0d67109 100644
> > --- a/drivers/mmc/host/sdhci-uhs2.h
> > +++ b/drivers/mmc/host/sdhci-uhs2.h
> > @@ -210,5 +210,6 @@
> >  struct sdhci_host;
> >  
> >  void sdhci_uhs2_dump_regs(struct sdhci_host *host);
> > +void sdhci_uhs2_reset(struct sdhci_host *host, u16 mask);
> >  
> >  #endif /* __SDHCI_UHS2_H */
> > diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> > index d4a57e8c9bb8..af336bdb4305 100644
> > --- a/drivers/mmc/host/sdhci.c
> > +++ b/drivers/mmc/host/sdhci.c
> > @@ -195,13 +195,14 @@ static void sdhci_runtime_pm_bus_on(struct sdhci_host *host)
> >  	pm_runtime_get_noresume(host->mmc->parent);
> >  }
> >  
> > -static void sdhci_runtime_pm_bus_off(struct sdhci_host *host)
> > +void sdhci_runtime_pm_bus_off(struct sdhci_host *host)
> >  {
> >  	if (!host->bus_on)
> >  		return;
> >  	host->bus_on = false;
> >  	pm_runtime_put_noidle(host->mmc->parent);
> >  }
> > +EXPORT_SYMBOL_GPL(sdhci_runtime_pm_bus_off);
> >  
> >  void sdhci_reset(struct sdhci_host *host, u8 mask)
> >  {
> > diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
> > index d9d7a76cedc1..b9932423db08 100644
> > --- a/drivers/mmc/host/sdhci.h
> > +++ b/drivers/mmc/host/sdhci.h
> > @@ -831,6 +831,7 @@ static inline void sdhci_read_caps(struct sdhci_host *host)
> >  	__sdhci_read_caps(host, NULL, NULL, NULL);
> >  }
> >  
> > +void sdhci_runtime_pm_bus_off(struct sdhci_host *host);
> >  u16 sdhci_calc_clk(struct sdhci_host *host, unsigned int clock,
> >  		   unsigned int *actual_clock);
> >  void sdhci_set_clock(struct sdhci_host *host, unsigned int clock);
> > 
>